#include<iostream>
using namespace std;

int main(){
	int C1,C2;
	freopen("input.txt","r",stdin);
	cin>>C1>>C2;
	int C3=C2-C1;
	int h,m,s;
	C3=(C3+50)/100;
	h=C3/(60*60);
	m=(C3-h*60*60)/60;
	s=(C3-3600*h-60*m);
	printf("%02d:%02d:%02d\n",h,m,s);
}